>>w8ji Tom wrote:
>> A good meter is more reliable than a scope.
>BillW KB7YUM wrote:
>What does that mean? Meters have a longer MTBF than Oscilloscopes?
A longer MTBF, NO. Meters are viewed more reliable because when they
catch fire, it's not as spectacular in display. Don't need an ambient
light shields. Among other attributes. Like external power. Therefore
are less damaging to our heath, because they don't radiate x-rays,or a
quite as large magnetic field. This concerns many today living near
High tension wires, EMF ect you've read else where.
Bill, should you think of meters as the condom of measuring and then
you'll be on a better wavelength of understanding Tom's commentary.
Just wear a helmet. We don't want to see your obituary.
I surely hope this helps you practice safe measuring. Contrary to
popular belief aswell Hot wire meter movements react faster than
any wavelength of light. And our eyes don't see 60hz or above flicker.
Thats why Bird Meters are the best to use. Thier slugs spin faster
which I'll explain later.
>The waveform envelope is limited by filters to 3000 Hz, an audio limit.
>But does not the FCC regulations state that the power is to be measured
>over one RF cycle?
>At 30 Mhz = 33.3 nano-seconds
>At 1.8 Mhz = 555 nano-seconds
>The rise time of a system is related thus: BW x RISETIME = CONSTANT =
0.35
>0.35/3000 = 117 micro-seconds. The peak rectifier circuit time constant
>should be designed to get the information as quickly as possible ( but
not
>quicker) , so that subsequent following pulses are not ignored. If the
>rectifier time-constant is 40 micro-seconds, then in 3 time constants
most of
>the prior information will be bled off and the circuit will be ready for
the
>next pulse. Some of the circuits I have looked at had 15 millisecond
>time-constants. Somehow either I am missing something very simple or my
logic
>is faulty!
I'm sure it is faulty because sooner or later the electron
beams within a CRT are going to escape the vacuum and mess
up your focus and LAB table. Try picking up that many pixels?
Esspecially with such a small dot pitch. Meters don't have
this disadvantage. Some use glass covers but most you can replace
with Acrilic products which are just as clear.
Meters don't require the need to keep a dust pan and brush near
the LAB table. And who cleans up anyways? Thats why the power
company's use KWhr meters instead of KWhr O'scopes. Plus that
disk spinning is more fun to watch.
>I think Rich is using a good system. The bandwidth of the scope is more
>than adequate and will not miss in-between pulses. The FCC says power is
>measured over one RF cycle.
Good maybe. But meters are the wave of the future. And think I've
proven they are more fun to use and require way less education. We
have to make this pass time of ours more appealing to ADD inflicted
young. Missing in-between is totally wrong. Come on Bill. We know
infared waves exist because we get sunburned. Missing a few pulses
is like next to nothing. If we can gain a few more folks to pass
time with... Lets face it, it's really lonely around here.
That is a typo error Bill. It should read "power is measured while riding
a Harley cycle." The bandwidth of the meter is modified by using
different
sizes and textures of rubber bands, therefore in the reach of most
amateur
experimenters. And are easier to slip over a sprocket. And a simple
modification
to a Bird Meter to allow the slug to spin freely involves only the pin
sheered
off. And a couple wipes of sand glued on loose leaf paper. (Let the glue
dry
over night in your closet) Bill lets not forget that RF cycle went out of
buisness. Why dwell on the past.
Another useful benefit is rubber bands only cost 5 cents per hundred at
wallmart. CRT's cost hundreds of dollars and require permits to dispose
of. You decide
whats more dangerous a rubber band breaking or a CRT implosion?
All opinions above are my own. And Amateur opposed to scientific because
I'm not a licenced scientist. So there.
73, Jerry krr2ak@juno.com
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